We propose to study the effects of Human Immunodeficiency Virus (HIV) and Human Lymphotropic Virus Type 1 (HTLV-I) infections on pregnancy in 3000 Haitian women and their offspring followed through 24 months of age. Preliminary studies indicate that 8% to 9% of pregnant women in this population have been infected with HIV and 10% with HTLV-I. We will evaluate potential risk factors contributing to the high prevalence of retrovirus infections in this population including sexual contacts, blood transfusions, and injections administered in clinics and by lay personnel. Blood specimens will be obtained from women in early and mid pregnancy, at delivery and at one and two years after delivery. Cord blood will be obtained and infants will be bled at 3 month intervals until 24 months of age. Trained community health workers will assure active follow-up of participants in a primary health care program with an established record for conducting community based studies. We will determine the effect of HIV and HTLV-I infections on the outcome of pregnancy (abortions, stillbirths and birthweight); infant growth; neonatal, infant. and two year mortality; and the safety and immunogenicity of BCG and measles vaccinations. The results of this study will define the rate of infection in infants born to seropositive women and identify factors that might be associated with a) the efficiency of maternal-infant transmission of HIV and HTLV-I, b) the acquisition of HIV and HTLV-I infections by women after delivery, and c) the acquisition of retrovirus infections in early childhood for infants born to seronegative women. We will identify serologic criteria for differentiating passive maternal antibodies from active HIV and HTLV-I infections in early infancy and we will determine the time from birth to onset of clinical disease in infected infants. The results of this prospective cohort study will help to define the epidemiology and natural history of HIV and HTLV.I infections in a high risk developing country population. The quantitative data will assist health care providers to develop strategies for the control of HIV and HTLV-I in this and similar populations throughout the world.